docs: def findAllBycolumn(self, target):
          """ Returns an array of columns in the region (defined by the raster), each
          column containing all matches in that column for the target pattern. """
          column_matches = []
          for column_index in range(self._raster[1]):
              column = self.getRow(column_index)
              column_matches[column_index] = column.findAll(target)
          return column_matches